The present invention relates to a multilayer printed circuit board. More to particularly, this invention relates to a multilayer printed circuit board which enables needless radiation of electromagnetic wave to be suppressed for preventing electromagnetic interference.
Structural example of conventional multilayer printed circuit board is shown in FIGS. 1, 2, 3, and 4.
FIG. 1 is a sectional view showing one example of 4-layer printed circuit board by way of conventional example 1. In FIG. 1, the 4-layer printed circuit board is provided with a first signal wiring layer 111, a ground layer 112, a power supply layer 113, and a second signal wiring layer 114 in order from above. Interlayer insulation materials 115 to 117 are formed between these wiring layers 111 to 114. Further, a signal wiring 118 is arranged in the first signal wiring layer 111, a signal wiring 119 is arranged in the second signal wiring layer 114, a ground wiring 120 is arranged in the ground layer 112, and a power supply wiring 121 is arranged in the power supply layer 113.
In FIG. 1, if signal current flows through the signal wiring 118, return circuit current is induced in the ground wiring 120 of the adjacent ground layer 112 through the interlayer insulation material 115. A loop which is made by the signal wiring 118 and the ground wiring 120 is small, thus needless electromagnetic wave radiated from the loop is small.
FIG. 2 is a sectional view showing one example of conventional 6-layer printed circuit board by way of conventional example 2. The 6-layer printed circuit board is provided with a first signal wiring layer 131, a second signal wiring layer 132, a ground layer 133, a power supply layer 134, a third signal wiring layer 135, and a fourth signal wiring layer 136 in order from above. Interlayer insulation materials 137, 138, 139, 140, 141 are formed between these wiring layers 131 to 136. Further, a signal wiring 142 is arranged in the first signal wiring layer 131, a signal wiring 143 is arranged in the second signal wiring layer 132, a signal wiring 144 is arranged in the third signal wiring layer 135, a signal wiring 145 is arranged in the fourth signal wiring layer 136, a ground wiring 146 is arranged in the ground layer 133, and a power supply wiring 147 is arranged in the power supply layer 134.
In FIG. 2, if signal current flows through the signal wiring 143, a return circuit current is induced in the ground wiring 146 of the adjacent ground layer 133 through the interlayer insulation material 138. A loop which is made by the signal wiring 143 and the ground wiring 146 is small, thus needless electro-magnetic wave radiated from the loop is small.
FIG. 3 is a sectional view showing another example of 6-layer printed circuit board of conventional example 3. The 6-layer printed circuit board is provided with a first signal wiring layer 151, a ground layer 152, a second signal wiring layer 153, a third signal wiring layer 154, a power supply layer 155, and a fourth signal wiring layer 156. Respective interlayer insulation materials 157, 158, 159, 160, and 161 are formed between these wiring layers 151 to 156. Further, a signal wiring 162 is arranged in the first signal wiring layer 151, a signal wiring 163 is arranged in the second signal wiring layer 153, a signal wiring 164 is arranged in the third signal wiring layer 154, a signal wiring 165 is arranged in the fourth signal wiring layer 156, a ground wiring 166 is arranged in the ground layer 152, and a power supply wiring 167 is arranged in the power supply layer 155.
In FIG. 3, if signal current flows through the signal wiring 162 or 163, a return circuit current is induced in the ground wiring 166 of the adjacent ground layer 152 through the interlayer insulation material 157 or 158. A loop which is made by the signal wiring 162 or 163 and the ground wiring 166 is small, thus needless electro-magnetic wave radiated from the loop is small.
FIG. 4 is a sectional view showing one example of 8-layer printed circuit board of conventional example 4. The 8-layer printed circuit board is provided with a first signal wiring layer 181, a second signal wiring layer 182, a ground layer 183, a third signal wiring layer 184, a fourth signal wiring layer 185, a power supply layer 186, a fifth signal wiring layer 187, and a sixth signal wiring layer 188 in order from above. Respective interlayer insulation materials 189, 190, 191, 192, 193, 194, and 195 are formed between these wiring layers 181 to 188. Further, a signal wiring 196 is arranged in the first signal wiring layer 181, a signal wiring 197 is arranged in the second signal wiring layer 182, a signal wiring 198 is arranged in the third signal wiring layer 184, a signal wiring 199 is arranged in the fourth signal wiring layer 185, a signal wiring 200 is arranged in the fifth signal wiring layer 187, a signal wiring 201 is arranged in the sixth signal wiring layer 188, a ground wiring 202 is arranged in the ground layer 183, and a power supply wiring 203 is arranged in the power supply layer 186.
In FIG. 4, if signal current flows through the signal wiring 197 or 198, a return circuit current is induced in the ground wiring 202 of the adjacent ground layer 183 through the interlayer 190 or 191. A loop which is made by the signal wiring 197 or 198 and the ground wiring 202 is small, thus needless electro-magnetic wave radiated from the loop is small.
However, above-described respective conventional examples include following problems.
If signal current flows through the signal wiring 119 shown in above conventional example 1, the return circuit current is not induced in the power supply wiring 121 of the adjacent power supply layer 113 through the interlayer insulation material 117, but the return circuit current is induced anywhere distant ground. For this reason, the loop which is made by the signal wiring 119 and anywhere distant ground to which the return circuit current is induced becomes large. Furthermore, in the same manner thatxcx9cthe signal wiring 111 is connected to the signal wiring 114 by a through hole 122, the return circuit current is induced anywhere distant ground, thus the loop which is made by successive signal wiring 111, through hole 122, and signal wiring 114 and anywhere distant ground becomes large, there is the problem that needless electro-magnetic wave radiated from the large loop becomes large.
If signal current flows through the signal wiring 142, the signal wiring 144, or the signal wiring 145 shown in the above conventional example 2, the return circuit current is not induced in the signal wiring 143 of the signal wiring layer 132 which is arranged adjacently through each interlayer insulation material 137, 140, or 141, further the return circuit current is not induced in the power supply 147 of the power supply layer 134, furthermore, the return circuit current is not induced the signal wiring 144 of the signal wiring layer 135, but the return circuit current is induced anywhere in the distant ground. For that reason, the loop which is made by the signal wiring 142, 144, or 145 and anywhere distant ground to which the return circuit current is induced becomes large. In the same manner when at least more than two of the signal wiring 142, 143, 144, and 145 are connected by the through hole 148, the return circuit current is induced anywhere in the distant ground. The loop which is made by at least more than two of the successive signal wiring 142, 143, 144, and 145 and the through hole 148, and anywhere distant ground becomes large, thus there is the problem that needless electro-magnetic wave radiated from these loops becomes large.
If signal current flows through the signal wiring 164, or the signal wiring 165 shown in the above conventional example 3, the return circuit current is not induced in the power supply wiring 167 of the power supply layer which is arranged adjacently through each interlayer insulation material 160, or 161, but the return circuit current is induced anywhere in the distant ground. For that reason, the loop which is made by the signal wiring 164, or 145 and anywhere distant ground to which the return circuit current is induced becomes large. In the same manner when at least one of the signal wiring 164, and 165 is included, and a signal wiring of different signal layer is connected by the through hole 168, the return circuit current is induced anywhere in the distant ground. The loop which is made by the signal wiring including at least more than one of the signal wiring 164, and 165 and the through hole, and anywhere distant ground becomes large, thus there is the problem that needless electro-magnetic wave radiated from these loops becomes large.
If signal current flows through the signal wiring 196, 199, 200, or 201 shown in the above conventional example 4, the return circuit current is not induced in the signal wiring 197, power supply wiring 203, and the signal wiring 200 which are arranged adjacently through each interlayer insulation material 189, 193, 194, or 195, but the return circuit current is induced anywhere in the distant ground. For that reason, the loop which is made by the signal wiring 196, 199, 200, or 201 and anywhere distant ground to which the return circuit current is induced becomes large. In the same manner when at least more than one of the signal wiring 196, 199, 200, or 201 is included, and a signal wiring of different signal layer is connected by the through hole 204, the return circuit current is induced anywhere in the distant ground. The loop which is made by the successive signal wiring including at least more than one of the signal wiring 196, 199, 200, or 201 and the through hole 204, and anywhere distant ground becomes large, thus there is the problem that needless electro-magnetic wave radiated from these loops becomes large.
In view of the foregoing, it is an object of the present invention, in order to overcome the above-mentioned problems, to provide a multilayer printed circuit board which can suppress needless electro-magnetic radiation.
According to a first aspect of the present invention, in order to achieve the above-mentioned object, there is provided a multilayer printed circuit board which comprises at least two wiring layers in which a signal wiring and/or a power supply wiring for constituting an advance circuit current route of a signal and/or a power supply is mixed, and at least two ground layers in which at least one of them is arranged adjacently to the respective all-two wiring layers, wherein a return circuit current route of the signal and/or the power supply toward the ground layer is secured.
According to a second aspect of the present invention, there is provided a multilayer printed circuit board, in the first aspect, wherein the multilayer printed circuit board comprises a signal and/or a power supply through-hole for connecting interlayer of the signal wiring and/or the power supply wiring in at least two wiring layers continuously, and a through-hole for connecting at least two of the ground layers each other existing adjacently to the signal and/or the power supply through-hole, thus continuous return circuit current route is secured with respect to the advance circuit current route of the at least two wiring layers.
According to a third aspect of the present invention, in the first or the second aspect, there is provided a multilayer printed circuit board, wherein the multilayer printed circuit board is provided with an interlayer insulation material for ensuring insulation for each wiring between at least two ground layers in at least two wiring layers.
According to a fourth aspect of the present invention, in any of the first to the third aspect, there is provided a multilayer printed circuit board, the multilayer printed circuit board has a relationship of position between at least two wiring layers and at least two ground layers that at least four-layer of layer-built constitution is made by a mixed wiring layer of a first signal and/or a power supply wiring, a first ground layer, a second ground layer, and a mixed wiring layer of a second signal and/or a power supply wiring in order of above layer-built constitution.
According to a fifth aspect of the present invention, in any of the first to third aspect, there is provided a multilayer printed circuit board, the multilayer printed circuit board has a relationship of position between at least two wiring layers and at least two ground layers that at least four-layer of layer-built constitution is made by a mixed wiring layer of a first signal and/or a power supply wiring, a first ground layer, a mixed wiring layer of a second signal and/or a power supply wiring, and a second ground layer, in order of above layer-built constitution.
According to a sixth aspect of the present invention, in any of the first to the third aspect, there is provided a multilayer printed circuit board, the multilayer printed circuit board has a relationship of position between at least two wiring layers and at least two ground layers that at least six-layer of layer-built constitution is made by a mixed wiring layer of a first signal and/or a power supply wiring, a first ground layer, a mixed wiring layer of a second signal and/or a power supply wiring, a mixed wiring layer of a third signal and/or a power supply wiring, a second ground layer, and a mixed wiring layer of a fourth signal and/or a power supply wiring in order of above layer-built constitution.
According to a seventh aspect of the present invention, in any of the first to the third aspect, there is provided a multilayer printed circuit board the multilayer printed circuit board has a relationship of position between at least two wiring layers and at least two ground layers that at least eight-layer of layer-built constitution is made by a mixed wiring layer of a first signal and/or a power supply wiring, a first ground layer, a mixed wiring layer of a second signal and/or a power supply wiring, a mixed wiring layer of a third signal and/or a power supply wiring, a second ground layer, a mixed wiring layer of a fourth signal and/or a power supply wiring, a third ground layer, and a mixed wiring layer of a fifth signal and/or a power supply wiring in order of above layer-built constitution.
The above and further objects and novel features of the invention will be more fully understood from the following detailed description when the same is read in connection with the accompanying drawings. It should be expressly understood, however, that the drawings are for purpose of illustration only and are not intended as a definition of the limits of the invention.